Suppressor-type antenna



P 1958 M. w. SCHELDORF 2,852,774

SUPPRESSOR-TYPE ANTENNA 4 Sheets-Sheet 1 Filed Aug. 11, 1955 up m Sept. 16, 1958 M. w. SCHELDORF 2,852,774

SUPPRESSOR-TYPE ANTENNA Filed Aug. 11, 1955 4 Sheets$heet 2 Sept. 16, 1958 M. w. SCHELDORF 2,352,774

SUPPRESSOR-TYPE ANTENNA Filed Aug. 11, 1955 4 Sheets-Shet 4 I: V 4 L26 ammrzsr wmzimzk/ay difm/vrqy atent A 2,852,774 Patented Sept. 16, 1958 2,852,774 surrnnsson-rrrn ANTENNA Marvel W. Scheldorf, Palos Heights, 11]., assignor to Andrew Corporation, a corporation of Illinois Application August 11, 1955, Serial No. 527,842

11 Claims. (Cl. 343841) in order to obtain satisfactory beam width reduction.

Various attempts have been made to reduce the number of feed points by utilizing end-fed arrays, both with and without phase inverters. Some of the methods evolved simply provide multiple feed points in a simplified manner. One of the most successful methods employs a solid dielectric insulation between a central feed wire and coaxially mounted cylinders. The dielectric insulation used in this method adds losses and extra weight, and there is some question about the feasibility of providing good bonds between the material and the conductors so as to avoid moisture problems. Another method employs phase inverters illustrated in U. S. Patent No. 1,957,949 by Franklin, in which the destruction portions of the standing waves of current are set up to cancel out in quarter-wave sections oriented, in one embodiment, normal to the general direction of the radiating conductor. Each of these folded portions produces the 180 phase delay desired, but it also provides a detrimental impedance situation at the base of the quarter wave stub, since the low loss conductors in the stub will cause the impedance at the base of the stub to approach infinity near the resonant frequency of the stub. As a result there is no current coupling between adjacent stub-separated sections of the antenna. Coupling between adjacent sections is, therefore, obtained by inductive and radiation coupling, and since the coefiicients of coupling by these means are very low, those sections further remote from the feed points of the antenna radiate considerably less energy than those adjacent to the feed points, giving highly tapered illumination. With such a highly tapered illumination the main beam is far wider than desired, and the side lobes are blended into the main beam to produce an unwanted characteristic pattern. The overall result is that the gain from such an antenna is far below that desired.

The present device solves the just discussed problem in a new and unique fashion. It is obvious that radiation currents do not have to exist along the entire length of an antenna conductor system, and quite successful radiation patterns can be secured with arrays of co-linear halfwave dipole antennas with end-to-end spacings of a half Wavelength. For long arrays of this type the spacing between half-wave antenna radiators causes a loss of only one db in the gain of the antenna compared with an array of the same length Where the dipole antennas are mounted end-to-end without the spacings between them. The array of co-linear half-wave dipole antennas with end to-end spacings of a half-wave length is equivalent to a conductor in which the normally destructive portions of the conductor have been rendered ineffective, that is, the radiation from the destructive portions of the conductor has been suppressed. The present invention, therefore, obtains a high gain antenna by suppressing the radiation from the alternate half-wave sections of a wire radiator.

One well known method of suppressing radiations from a wire radiator is by means of a concentric shield over the conductor. It has been foundthat sleeves of this character, alone, are unsatisfactory because the outer surfaces are resonant and radiate almost as badly as the unshielded conductor. To prevent the concentric shields from bearing radiation currents, the present device adds additional quarter-wave length sleeves over the concentric shields surrounding the center conductor. These quarter-wave length sleevesare arranged in opposition so as to producetwo balanced high impedance points centrally located on the outside of their inner concentric If this is done, each of the sleeve antenna secsleeve. tions now becomes, in effect, a one-to-one transformer,

which will to a high degree suppress-any radiation from the outer surface of theti'ansformer antenna section. Close coupling is at the same time maintained between the active radiating sections by virtue of the currents along the center conductor so that the magnitude of the radia tion from the several radiating sections is approximately equal.

Accordingly, it is an object of this invention to provide a new and improved high gain antenna.

Another object of this invention is to provide an improved multiple half-wave length antenna in which only certain desired half-wave length sections act as radiators.

A further object of this invention is to provide an improved multiple half-Wave length antenna in which radiation suppressors prevent radiation from certain ofthe half-wave length antenna sections.

Other objects and advantages of the invention will be apparent during the course of the following description when read in connection with the accompanying drawings, wherein:

Figure lshows a two suppressor array of an antenna embodying the present invention, taken partly in cross section; V

Figure 2 is an enlarged partial cross-sectional view of the radiation suppressor structure of the antenna of Figure 1; f

Figure 3 is an end view of a radiation suppressor showing the manner in which the insulating spacer is inserted between the radiation suppressor structure and the center conductor; 7

Figure 4 isan enlarged, partially cutaway, cross-sectional view of the feed point structure of Figure 1;

Figure 5 shows a square loop antenna having two radiation suppressors;

Figure 6 shows the E-plane characteristic pattern for the square loop antenna of Figure 5;

Figure 7 is a schematic diagram of a four suppressor antenna array embodying the suppressor structure of this invention;

Figure 8 shows the E-plane characteristic radiation pattern for the four suppressor array of Figure 7;

Figure 9 shows the application of the present inven-' tion to a vertical. antenna array; and

Figure 10 is a detail view of the feed point structure of Figure 9.

Referring now more particularly to Figures 1 through 4, there is shown an antenna consisting of two hollow center conductors 10 and 11 which are axially aligned but separated from one another at the center of the antenna by an electrical insulator block 12. An antenna feed cable 13 has one of its conductors 14 connected to the hollow center conductor 10 by means of a screw 15 which passes through a hole 16 in the insulating block 12 and is threaded into a boss 17 of the conductor 10. The other conductor 18 of the feed cable 13 is similarly connected by means of a screw 19 which passes through a hole 21 in the insulating block 12 and is threaded into a boss 22 of the conductor 11.

Spaced a half-wave length from the block 12 are two radiation suppressors 26, each of which is approximately 3 a half-wave length long. Each'radiation suppressor 26 consists of a half-wave length inner sleeve- 27 and two outer sleeves 28. Each outer sleeve has a mechanical length slightly less than a quarter-wave length and is positioned concentric with the inner sleeve. The inner sleeves. 27 are concentrically mounted with the center conductors and 11 and spaced therefrom by insulators 29.

Attached along the conductors 10 and 11 are paired tabs 31, 32'and 33, 34 shown in Figures 2 and 3. pair of tabs 31 and 32 are positioned in the same plane 180 displaced from one another. A pair of tabs 33 and 34 are spaced from each pair of tabs 31 and 32 a distance slightly larger than the spacer 29 and in the same plane 180 displaced from each other. Two tabs 35' and 36 are positioned in the same plane as tabs 31 and 32 along a straight'line' drawn through tabs 31 and 32, and are connected to inner sleeve 27. Two tabs 37 and'38 are positioned inthe same plane as tabs 33 and 34 on a line drawn through .these tabs, and are connected to the-inner sleeve 27. The spacer 29 has two notches 39, 40 positioned 180 apart along its inner perimeter, and two notches 41,42180" displaced along its periphery on a straight line drawn through the inner notches. The spacers 29 are inserted over the tabs 37, 33, 34, 38 and then rotated so as to be firmly locked between the two planes of tabs.

The outer quarter-wave sleeves 28 are mechanically and electrically connected to the inner sleeve27 by conductive rings 44. Generally the rings 44 are brazed to theinner sleeve 27, and the outer sleeves 28 are then connected by means of set screws 45 to the rings 44. Other means of connection may of course be used. Electrically the sleeves 28 are one quarter-wave length long due to the end rings 44;

The number of radiation suppressors 26 used fora particular antenna will depend upon the total length of the antenna. Since it is desired to suppress radiation from the antenna conductor every other half-wave length, it becomes obvious that a suppressor 26 must be installed at such sections of the antenna length. To provide protection from weather and to further support the structure,

an insulating tubular casing, not shown, surrounds the antenna from end to end.

In operation, the antenna is fed from the feed cable 13 which excites the antenna conductors 10 and 11 to radiate along their lengths. Dueto the existence of the radiation suppressors 26, only those halt-wave lengths along the length of the antenna which are desired' to radiate energy into space will do so.

To illustrate in greater detail the teaching of the pres ent invention, typical dimensions-for a particular antenna embodiment to operate at 460 me. willbe given. The antenna rods 10 and 11 were inch hollow tubing each- 3l.875 inches long, separated by A inch by the insulator sleeve and support member 12. .The conductor sleeves 27 each were of 2 inch diameter 12% inches long, while the outer sleeve portions 28 were of 2 /2 inch diameter. The insulator spacers 29 were inch thick.

Referring to' Figure 5, there is shown the electrical line diagram for a square loop antenna utilizing the radiation suppressor 26 to suppress radiation along two of its half-wave length sides. The radiation. pattern in the E-plane obtained for this antenna using the radiation suppressors is shown by the curve A in Figure 6, and as is readily, seen is far superior to that for a square loop shown by the curve B without the use of suppressors.

Figure 7 shows a schematic line diagram of an antenna similar to that of Figure .1 using four radiation suppressors for the array. In the half-wave length portions at'eacli end, the representation for the central conductor hasbeen shown broken because of space limitations on'the drawing sheet. The central conductor actually is continuous. Again the radiation pattern for the E-plane sliown in Figure 8 shows a-substantial improve- Each ment in the beam width, and, by reason of lower powered secondary lobes;'in' the overall gain of the antenna.

Thus, the four suppressor array of Figure 7 may be extended into a six, eight, etc. suppressor array, and the suppressor structure utilized in combination with the antennas shown may be utilized with other antenna arrays and configurations. The showing of a limited number of antenna configurations to which the suppressor structure of this invention is applied should not be construed to limit the applicability of the radiation suppressors used herein.

While the application of the invention thus far has been directed primarily to horizontal antennas, the invention is applicable to vertical antennas as illustrated in Figures 9 and 10 of the drawings. It will be noted that the antenna in Figure 9 has a central tubular conductor structure 60 which is provided at half-wave length intervals with a plurality of suppressors 26 corresponding in structure to those previously described in connection with the preceding figures of the drawings. Removed from an upper suppressor 26 by a quarter-wave length is a structure which is the feed structure for an arrangement of this type. This structure is shown in detail in Figure 10. The structure 50 comprises split cylindrical elements 51 and 52 having an overall length of a half-wave length. The split cylinder 51 adjacent the lower end is provided with a short-circuiting bar 53, and in a similar manner the split cylinder 52 is provided at its opposite end with a short-circuiting bar 54. These bars 53 and 54 may be moved along the slot to tune the feed arrangement. A coaxial conductor 55, having an outer conductor 56 and an inner conductor 57, extends upwardly within the tubular structure to just below the split cylinder 51 where it passes through a suitable opening in the tubular conductor 60. The inner conductor 57 is connected by a conductor 58 to the lower edge of the split cylindrical member 52 diametrically opposite the slot thereof, and the outer conductor 57 is connected by a conductor 59 to the top edge of the split cylindrical member 51 diametrically opposite the slot thereof. The arrangement of having the coaxial conductor within a cylindrical conductor 60 has the advantage of providing lightning protection. The entire structure shown in Figure 9 furthermore is encased in a weather-proof insulated cylindrical casing which also assists in increasing the rigidity of the entire structure, and thus providing adequate support. This is an extension of the teachings inmy copending patent application Serial No. 312,235 filed September 30, 1952 for a Broad BandrAntenna, now Patent'2,754,514.

The antenna arrangement shown in Figure 9 is intended to illustrate a' vertical antenna having a plurality of suppressor elements 26 and a feed element 50. While two suppressor elements 26 have been shown below the feed element 50, it would be obvious that two suppressor elements 26 would be located above this element. In other words, the feed element 50 is midway between the total number of suppressor elements 26 whether they are four in number, six, eight, or a greater number. Located a halt-wave length below the lower suppressor 26 is a radiation choke 70. A construction for such a radiation choke is explained in detail in my copending patent application Serial No. 540,239 filed October 13, 1955. This radiant choke keeps the radiant energy from travelling down the mast below this point.

While the suppressor structure shown in the drawings would appear to bear some resemblance to the structure shown in the Greene Patent No. 2,486,597, there is no similarity in an electrical sense since the Greene patent utilizes the sleeves as radiator elements. In contrast thereto, applicant uses these elements as suppressor elements. Thus, the operation is entirely different,

providing many advantages over the arrangements heretofore found in the prior art.

While there has been shown and described an invention in connection with certain specific embodiments, it will, of course, be understood that it is not intended nor Wished to be limited thereto since it is apparent that .the principles herein disclosed are susceptible of numerous other applications, and modifications may be made in the circuit arrangement and in the instrumentalities employed without departing from the spirit and scope of this invention as set forth in the appended claims.

I claim as my invention:

1. An antenna comprising a multi-half-wave length radiator and a plurality of radiation suppressors positioned along selected half-wave lengths of said radiator to suppress radiation from said selected half-wave lengths to improve the overall gain of said antenna the suppressors comprising inner and outer conductors substantially surrounding the radiator, the inner being one-half wavelength long and the outer comprising aligned spaced segments each approximately one-quarter wavelength long and having the ends of the outer conductively connected to the ends of the inner.

2. An antenna comprising two conductors positioned end to end in insulated engagement and fed at their common center, a plurality of half-wave length inner sleeves coaxially positioned along said conductors, a first quarterwave outer coaxial sleeve extending conductively from one end of each of said inner sleeves, a second quarterwave outer coaxial sleeve extending from the other end of each of said inner sleeves, the ends of each of said coaxial outer sleeves extending conductively from said inner sleeves being positioned to present a high impedance to radiation, said sleeves being positioned along alternate half-wave length portions of said conductors.

3. An antenna comprising a central conductor fed with radiation-producing currents, at least one half-wave length inner sleeve positioned in spaced coaxial insulated relationship to said conductor, a first quarter-wave outer sleeve extending conductively from one end of said inner sleeve and concentric therewith, a second quarterwave outer sleeve extending conductively from the other end of said inner sleeve and concentric therewith, the adjacent ends of said outer sleeves being positioned to present a high impedance to radiation, said sleeves being positioned along an out-of-phase radiating portion of said antenna.

4. An antenna radiation suppressor adapted to shield a half-wave length of antenna conductor comprising a spaced coaxial sleeve for the antenna conductor, said sleeve being one-half wave length long, and a pair of coaxial sleeves surrounding said first sleeve in spaced relation thereto, each of said latter sleeves being effectively one-quarter wave length long and extending conductively from each end of said first sleeve toward the center thereof, the adjacent ends of said latter sleeves producing balanced high impedance points at the center and on the outside of said first sleeves.

5. An antenna radiation suppressor for an antenna conductor comprising a spaced coaxial shield for the antenna conductor, said shield being one-half wave length long, and a pair of coaxial shields surrounding said first shield in spaced relation thereto, each of said latter shields being effectively one-quarter wave length long and extending conductively from each end of said first shield toward the center thereof, the adjacent ends of said latter shields producing balanced high impedance points at the center and on the outside of said first shield.

6. An antenna array comprising a linear dipole connected to a source of radiant energy, each conductor of said dipole being at least a wave length long, and a plurality of radiation shields for said conductors, each shield being a half-wave length long, and being spaced at half-wave length intervals along said conductor, each radiation shield comprising a radiation suppressor as set forth in claim 5.

7. An antenna comprising a vertical radiating conductor, a plurality of radiation suppressors positioned along selected half-wave lengths of said conductor to suppress radiation therefrom at half-wavelength intervals, a pair of cylindrical members located midway between said suppressors, said cylindrical members each having a longitudinal slit and being one-quarter wave length long, a shorting member connected across the edges of each slit of the cylinder, and means for supplying radiant energy to said cylinders at their adjacent end edges diametrically opposite to the edges of the slit.

8. An antenna comprising a vertical radiating conductor having a plurality of radiation suppressors positioned along selected half-wave lengths thereof to suppress radiation at half-wave length intervals, a pair of cylindrical members located in insulated relation to each other between said suppressors, said cylindrical members having a longitudinal slit and an overall length of onehalf wave length, a shorting member connected across the edges of the slit of each cylinder adjacent the remote end thereof, and means for supplying radiant energy to said cylinders at their adjacent end edges diametrically opposite to thev edges of the slit.

9. An antenna comprising a hollow vertical radiating conductor having a plurality of radiation suppressors positioned therealong to suppress radiation therefrom at half-wave length intervals, means for preventing mast coupling and for eliminating mast currents comprising a pair of cylindrical members located in insulated abutment to each other between said suppressors, said cylindrical members having a longitudinal slit and an overall length of one-half wave length, a shorting member,

connected across the edges of the slit of each cylinder, said cylindrical members being connected to two conductors supplying radiant energy to said antenna.

10. An antenna comprising a hollow vertical radiating conductor having a plurality of radiation supressors positioned therealong to suppress radiation at halfwave length intervals, a pair of cylindrical members located in insulated abutment to each other between suppressors, said cylindrical members having a longitudinal slit and an overall length of one-half wave length, a shorting member connected across the edges of the slit of each cylinder adjacent the remote end thereof, and means for supplying radiant energy to said cylinders at their adjacent end edges diametrically opposite to the edges of the slit, said means comprising a coaxial conductor located within said hollow vertical radiating conductor and extending to the exterior thereof adjacent the lower edge of said cylindrical members, each said member being connected to a diflerent one of the conductors of said coaxial conductor.

11. A suppressed-radiation assembly comprising a radiating conductor of greater than one-half wavelength having a half-wavelength portion thereof effectively surrounded by a radiation suppressor, the suppressor comprising inner and outer conductors substantially surrounding the radiator, the inner being one-half wavelength long and the outer comprising aligned spaced segments each approximately one-quarter wavelength long and having the ends of the outer conductively connected to the ends of the inner.

References Cited in the file of this patent UNITED STATES PATENTS 2,113,136 Hansell Apr. 5, 1938 2,237,792 Roosenstein Apr. 8, 1941 2,323,641 Bailey July 6, 1943 FOREIGN PATENTS 307,059 Great Britain Dec. 24, 1929 

